A portable device such as a portable phone, a PDA (personal digital assistants), and a note PC, when operating on the battery, may have varying battery life depending on its power consumption.
In recent years, there has been an increasing number of portable devices employing a multitask OS. Some of the portable devices employing a multitask OS may allow client software (i.e., rich software) having rich functions, rich user-interface expressiveness and operability, and rich displayed contents or the like to be added.
However, a portable device employing a multitask OS may needlessly consume electric power due to the continuous operation of rich software. A smart phone, which is an example of portable devices employing a multitask OS, has large power consumption.
A smart phone is widely used for various purposes in addition to the purpose of making a phone call. A smart phone may be used for viewing or using SMS (Short Message Service), MMS (Multimedia Messaging Service), mail such as Internet mail, Web, news, blogs, maps, traffic information, etc., as well as for playing games.
Applications such as rich software added for the purpose of implementing other functions in addition to the phone function of a smart phone may not be guaranteed to operate in conformity with the intention of hardware designers. Third-party application designers implementing software rely on the external specifications of hardware, and, thus, may not voluntarily pay attention to power consumption. Also, third-party application designers may not be positively conscious of the operations of applications designed by other application designers.
Moreover, even when a smart phone is not being operated by a user, its software and hardware constantly operate for the purpose of receiving mail, updating RSS (RDF Site Summary), searching for wireless devices (e.g., through 2G/3G/LTE, Wi-Fi, Bluetooth, infrared, etc.), and sensing (e.g., sensing for GPS, motion sensing, geomagnetism sensing, temperature sensing, light sensing, etc.).
In order to reduce power consumption, some portable devices known in the art prohibit tasks (i.e., processes) to operate in parallel, and allow only minimum necessary processes to operate in a standby state. Some related-art mobile devices known in the art conserve battery power by taking into account every aspect inclusive of applications (see Patent Document 1, for example).
Since application designers for related-art portable devices are not positively conscious of the operations of other applications, however, power reduction in one application may not produce a sufficient result due to influence from other applications.
FIG. 1 is a drawing illustrating an example of power consumption in a related-art portable device. FIG. 1 illustrates transitions of power consumption made by an application 1, an application 2, an OS 3, and a device 4. The application 1 operates at a polling interval T1. The application 2 operates at a polling interval T2. Namely, the applications 1 and 2 operate at predetermined intervals.
However, the operations of the applications 1 and 2 are unrelated to and independent of each other. It is assumed that there is no process other than the application 1 and the application 2. The application 1 and the application 2 use the device 4 that is their hardware resource. Further, it is assumed that the powers consumed by the application 1 and the application 2 are responsive to the time lengths of their respective accesses to a CPU or memory. The CPU enters the low power consumption state when all the processes are in the standby state.
The OS 3 and the device 4 exhibit large power consumption during the periods in which the application 1 and the application 2 operate. In the example illustrated in FIG. 1, the sum of powers consumed by the application 1, the application 2, the OS 3, and the device 4 is 125 mW. The sum of powers consumed by the application 1, the application 2, the OS 3, and the device 4 can be reduced by shortening the period during which the OS 3 and the device 4 exhibit large power consumption.
However, the polling intervals T1 and t2 in this related-art portable device are determined by the application designers of the application 1 and the application 2 without taking into account the power consumption of the OS 3 and the device 4. Due to this reason, the period during which the application 1 and the application 2 operate cannot be adjusted in the related-art portable device so as to shorten the periods during which the OS 3 and the device 4 exhibit large power consumption.